Use audio_stream_type_t consistently

Change-Id: I1e92f018a07e4b1b73ef8d4de461ef1e08bc48e7
diff --git a/modules/audio/audio_policy.c b/modules/audio/audio_policy.c
index 409f0a1..3313d48 100644
--- a/modules/audio/audio_policy.c
+++ b/modules/audio/audio_policy.c
@@ -201,7 +201,7 @@
     return -ENOSYS;
 }
 
-static bool ap_is_stream_active(const struct audio_policy *pol, int stream,
+static bool ap_is_stream_active(const struct audio_policy *pol, audio_stream_type_t stream,
                                 uint32_t in_past_ms)
 {
     return false;